Apparatus for automatic analyzing



June 1, 1965 Filed April 19, 1960 C. C. HACH APPARATUS FOR AUTOMATIC ANALYZING 2 Sheets-Sheet 1 INVENTOR.

Clifford 6'. hac/r June 1, 1965 c. c. HACH APPARATUS FOR AUTOMATIC ANALYZING 2 Sheets-Sheet 2 Filed April 19. 1960 INVENTOR. Clifford 6. hac/z United States Patent 3,186,799 APPARATUS FQR AUTQMA'EliI AIJALYZEIG Clifford C. Hash, Ames, lowa, assignor to Each Chemical ompany, AHEES, Iowa, a corporation of lawn Filed Apr. 19, 19%, Ser. No. 23,245 12 Claims. (Cl. 23-253) The present invention relates to methods and devices for making chemical analyses and concerns, more particularly, methods and analyzers capable of automatically and continuously performing any one of a wide variety of chemical tests.

It is the primary aim of the invention to provide an analyzing method and automatic analyzers which obviate the necessity for manually performing chemical analyses that are made as a routine check of some process. For example, in water treatment plants, analyzers practicing the present invention can be used to test for residual chlorine, pH fluorides, alkalinity, total hardness or a desired hardness level, and thus provide information as to the operation of the plant without requiring the services of a trained person. The analyzers of the invention thus free plant personnel from routine testing jobs and minimize the possibility of human error.

Moreover, analyzers embodying the invention are capable of routinely performin titrarnetric analyses so that a wide variety of chemical analyzing tasks can be handled, all on an automatic basis. Indeed, analyzers constructed in accordance with the invention can be used to perform any spectrophotometric titration or simple colorimetric test in which the sample is reasonably clear and no precipitate is formed.

Another object of the invention is to provide an automatic analyzer and method of analyzing of the above character which function on a continuously flowing fluid sample so as to make continuous testing possible.

it is also an object to provide an automatic analyzer, as described above, which is quite accurate and very reliable, needing little or no routine maintenance other than periodic replenishing of the test solutions being used. It is a collateral object to provide an automatic analyzer of this type which is inexpensive to manufacture and operate, particularly because of a relatively simple design using few moving parts such as pumps or valves.

A further object is to provide an automatic analyzer that is very convenient to use, both as to setting up the unit for performance of a particular test and reading or recording the results of the testing.

It is still another object to provide an automatic analyzer which is exceptionally versatile in that a wide variety of tests can be performed and that the test information can be displayed, recorded or used in a variety of ways.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

FIGURE 1 is a diagrammatic representation of an automatic analyzer constructed in accordance with the present invention;

FIG. 2 is a diagrammatic representation of a modified form of automatic analyzer particularly intended for spectrophotometric titration; and

FIG. 3 is a schematic wiring diagram of the circuit utilized in the analyzer shown in FIG. 2.

3,186,799 Patented June 1, 1965 "ice Turning first to FIG. 1 there is schematically shown an analyzer it for performing the method of, and constructed in accordance with, the invention. The particular mbodiment shown in this figure is intended for continuous colorimetric testing of a fluid sample 11 by using measured quantities of a known fluid reagent 12.

in accordance with the invention, the method of testing includes the steps of creating a steady and uniform stream of the sample 111, adding to the stream a predetermined and uniform fiow of the reagent 12, mixing the sample and reagent, flowing the mixture constantly and uniformly through a cell, and detecting any reaction caused by mixing the measured quantities of sample and reagent in the cell. In the preferred FIG. 1 embodiment, the reaction is detected by a colorimeter 15 whose electrical output is indicated by a galvanometer 16. The galvanometer 16 gives a continuous reading reflecting the extent of color change produced by the reaction of the sample it and reagent 12 in the colorimeter 15. Hence, by knowing tne nature and concentration of the reagent 12, and the amounts of sample and reagent being continuously brought together, the analyzer 1t accurately indicates the presence and concentration of the unknown in the sample under test.

To carry out the invention, the analyzer 19 includes apparatus for accomplishing continuously the several steps listed above so as to capably and automatically perform the method of the invention. In describing the preferred form of the analyzer 1d, specific values will be given as an aid to understanding the functions of the apparatus and although these values are used in commercial analyzers embodying the invention, it will be understood that the invention is not restricted to any one particular set of values.

Turning to the construction of the analyzer 10, in order to creme a steady and uniform stream of the sample 11, the sample is fed at a constant head pressure through a capillary metering tube 21. In the preferred construction, a conduit 22 conducts the sample through a flowcontrol cock 23 to a mixing passage 24. The metering tube 21, conduit 22 and passage 24 are all fixed relative to one another by a common frame 25. In the preferred apparatus, the metering tube 21 and the passage 24 are defined by suitably formed glass tubing which is embedded in a plastic frame block 26 that is effective to protect the glass parts and hold them in the desired relative positions.

To maintain a constant head pressure on the sample 11 in the passage 24-, an upstanding overflow outlet or passage 27 is mounted on the frame 25 in communication with the passage The fluid overflowing from the outlet 27 spills into a conduit 2 that is connected to a drain 3%. An open-top sight glass 23 is also provided to visually indicate the head of the sample. In a workable embodiment, the cock 23 is, adjusted to provide a sample flow of mls./ min. The capillary metering tube 21 is formed of such a length and diameter as to pass 5 rnls./ min. with the particular sample head established by the overflow outlet 27. The fluid sample which does not pass through the metering tube 21 is simply spilled through the overflow outlet 27 to the drain 30 as is shown by the flow arrows appearing in FIG. 1 in the passage 24.

For adding a steady and uniform stream of reagent 12 to the stream of the sample, the reagent is fedto thepassage 24 at a predetermined head pressure through a capillary metering tube 31. In the illustrated analyzer, the reagent 12 is contained in a five quart plastic bag 32 supported within a carton 33 and is fed to the metering tube through a conduit 34. A sight glass 35 provides a visual indication of the amount of reagent solution remaining in the bag 32.

To maintain a predetermined head pressure on the reagent 32, a float valve as is interposed in the conduit 34.

The float valve includes a chamber 37 having an upper valve inlet opening 38 and containing a float 39 which supports a plug 40 for closing the inlet 38. The float 39 is freely supported within the walls of the chamber 37 and is guided for vertical movement on an upstanding tube 41 secured in the bottom of the chamber 3'7. The tube 41 also serves as a discharge opening from the chamber.

In operation, the reagent 12 spills through the inlet 38 into the valve chamber 37 at a rate much faster than the reagent can be passed through the metering tube 31. As a result, the chamber 37 gradually fills, causing the float 39 to rise until the plug 49 closes the valve inlet 38. Thereafter, the level of the reagent 12 within the valve 36 remains constant. As soon as a small amount of reagent passes through the metering tube 31 and out of the chamber 37, the plug 40 slightly opens the inlet 33 and that amount of reagent is immediately replaced. As a result, a constant head pressure on the reagent at the metering tube isestablished. In the illustrated form of the analyzer,.the reagent head pressure and the length and diameter of the capillary metering tube 31 is selected so that a reagent flow rate into the passage 24 of 0.1 ml./min. is

established. It will also be noted that the head established by the float valve 35 is greater than the sample head established by the overflow outlet27 and thus the sample in the passage 24 is not forced upwardly through the capillary metering tube 31.

A disturbing problem which could affect the operation of the analyzer 10 is the presence of air bubbles Within the passage 24 and metering tubes 21,31. These air bubbles primarily result from air dissolved in the sample fluid which is released by the warming of the fluid as it passes into the room in which the analyzer is located or by the decrease in air solubility of the sample caused by the chemical reaction with the reagent 12. To minimize the effectof air bubbles, a strainer 45 is interposed in the passage 24 so that the fluid sample 11 must pass through the fine holes in the strainer before reaching the capillary metering tubes. This blocks the bubbles from the tubes 21, 31. Furthermore, the entire frame is tilted so that air bubbles tend to remain trapped at the end of the passage 24 adjacent the strainer 45 and the connection point of the sample conduit 22.

As for turbidity particles in the sample 11 or reagent 12, it has been found that by disposing the capillary metering tubes 21 and 31 in generally vertical directions and by establishing the fluid flow through these tubes from top to bottom, the tendency of turbidity particles to clog the tubes is greatly minimized.

For the purpose of mixin and briefly detaining the sample-reagent stream for colorimetric testing, the stream is dripped into a generally vertical transparent mixing cell 50 disposed in the colorimeter 15. The transparent cell 50 is formed with an open bottom and open top and is mounted in a surrounding transparent chamber 51 having an overflow outlet 52 disposed well above the open bottomof the cell 50. A nozzle 53 extends from the discharge end of the capillary metering tube 21 to a position over the open top of the cell 50 so that the sample-reagent stream is dripped downwardly into the cell 50 where it flows down through the cell, out the open bottom of the cell, up through the surrounding chamber 51, and out the overflow outlet 52. The mixture is then directed to a conduit 54 leading to the drain 30.

The dripping of the sample-reagent stream into the cell 50 causes complete mixing of the sample and the reagent, and the slow flow of the mixture down through the cell and up through the surrounding chamber 51 detains the mixture for colorimetric testing while maintaining a constant and uniform flow of the mixture under test Alternatively, mixing of the sample and reagent in the cell 50 can be accomplished by using a motor driven stirrer or some other mechanical device, in whichcasethe samplereagent stream need not be dripped into the cell.

To detect a color-producing reaction in the samplereagent mixture, the colorimeter 15 includes a lamp 60, condensing lens 61, shutter 62, color filter 63 and photoelectric cell 645, all arranged in the conventional manner to direct a beam of light through the fluid mixture passing downwardly through the celliStl. The output of the photoelectric cell 64- is coupled through an adjustable resistance 65 to the galvanometer 16. The wiring circuit also preferably includes a plug socket 66 coupled in parallel to the resistance 65 for permitting a continuous recorder to be added to the electrical circuit so that the output of the photoelectric cell 64 can be used to produce a continuous record.

Alternatively, the output of the colorimeter photoelectric cell 64 can be used to trip a relay for controlling another piece of apparatus. In this way the analyzer can perform as amonitor- For an example of this use of the analyzer It), the analyzer can be set up to automatically regenerate a zeolite-type of water softener. In such a use, the reagent 12 is an EDTA (ethylene diamine tetra acetic acid) plus pH buffer and an indicator such as Erio Chrome Black T solution with the amount of EDTA selected so as to reach the equivalence point and produce a color reaction at the desired hardness level at which the water softener is-to be regenerated. A red filter 63 is used in the colorimeter 1S and the sample conduit 22 is connected to the output of the water softener. As the waterv softener becomes less and less effective and the hardness of the water increases beyond the selected cut-in point, the sample-reagent mixture in the cell 50 turns from blue to red so that the photoelectric cell 64 is activated to produce a current. This current is then utilized to trip a relay and either sound an alarm or automatically begin regenerating of the Water softener.

By using appropriate reagents 12, the analyzer 10 can also be used for detecting pH or residual chlorine levels in water. It will also 'beunderstood that more than one reagent can be added to the sample under test simply by using two or more reagent supplies with associated float valves and capillary metering tube assemblies. Such a two-reagent unit has been found suitable for testing fluoride levels in water using a Megregian Maier form of test reaction.

It is of significance to note that the reagent metering tube 31 opens into the passage 24 ahead or upstream of the metering tube 21. This enables the reagent 12 to include small amounts of an anti-mold and slime agent such as formaldehyde as well as a formulation for preventing mineral: deposits so as to resist fouling of both of the tubes 21 and 31. However, if tube fouling is not a problem, the analyzer 10 could obviously function properly with the reagent metering tube 31 opening into the sample stream below or downstream of the tube 21.

In accordance with a further aspect of the invention, the method of testing described above can be modified for continuously performing spectrophotometric titration by using a titrant as the reagent added to the sample stream, adding also a constant and uniform flow of an indicator, and alternately reducing and increasing the amount of titrant added to the sample stream so as to repeatedly bring the mixture in the colorimeter cell to end point. That is, the flow of titrant is continuously adjusted so that each time the indicator produces a color change showing that end point of the titration has been reached, the flow of titrant is reduced below the color change pro ducing end point. When the color change again reverses, the titrant flow is increased to again bring about an end point reaction.

By continuously increasing and reducing the proportion of titrant added to the steadily flowing sample so as to cause oscillating color changes in the sample-titrant-indicator mixture, a continuous titration is run on the flowing sample. By knowing the sample flow rate and the strength andcharacter of the titrant, and by noting the titrant flow rates required to produce the oscillating color changes, the results of the titration can be easily calculated.

To carry out this further aspect of the invention, an analyzer ltla shown in FIG. 2 is provided including apparatus for accomplishing continuously the several steps referred to above so as to capably perform the inventive method. In describing the analyzer 16a, those parts similar to those described in connection with the analyzer it) in FIG. 1 have been given identical reference numerals with the identifying sufiix a added.

The analyzer Ilia acts upon a sample 11a which is transmitted to a capillary metering tube 21a through a conduit 22a having a flow-control cock 23a. The sample 11:: passes from the cock 230 into a mixing passage 24a and through a strainer 45a. A frame 25a supports the metering tube 21a and the associated structure.

An overflow outlet 27a establishes the sample pressure head in the passage 24a and a conduit 29a is provided for carrying the overflowing sample to a drain opening Etta. A sight glass 28!: visually indicates the sample head.

For adding titrant 12a to the passage 24a, the titrant is supported in a bag 32a and is conducted through a'conduit 34a to a capillary metering tube 31a which opens into the passage 24a. A sight glass visually indicates the supply of titrant 12a remaining in the bag 32a.

To maintain a predetermined head pressure on the titrant 12a at the metering tube 310, a float valve 36a is interposed in the conduit 34a. The float valve 36:; functions internally as does the float valve 36 described above.

Also interposed in the conduit 34a is a filter 7b to prevent solid particles from being lodged in the capillary metering tube 31a.

In addition to the sample 11a and titrant 12a, an indicator 71 is also added to the stream under test. For adding the indicator 71 to the sample-titrant stream, a supply of indicator is disposed in a plastic bag 72 carried within a carton 73, and a conduit 74 couples the bag 73 to a capillary metering tube 75. Preferably, a filter 76 is interposed in the conduit 74. A sight glass 77 is provided to visually indicate the amount of indicator '71 remaining in the bag 72.

The head pressure on the indicator 71 and the length and diameter of the metering tube 75 are selected so that an indicator flow rate through the metering tube of about 0.1 ml./min. is achieved. This flow rate is not particularly critical and will vary as the indicator 71 empties from the bag 72. Of course, a valve similar to the valve in can be interposed in the conduit 74 if it is desired to stabilize the indicator flow rate. A conduit 78 connects the lower output end of the metering tube 75 to a nozzle 53a which feeds the sample-titrant-indicator stream to a colorimeter 15a.

For mixing and briefly detaining the fluid stream from the nozzle 53a in the colorimeter 15a, a vertical transparent cell 54in having an open top and open bottom, surrounded by a transparent chamber Sla having an overflow outlet 52a, is provided. The overflow outlet empties into a conduit 54a which leads to the drain 3%. The colorimeter 15a includes a lamp 6%, condensing lens 61a, shutter 62a, filter 63a and photoelectric cell 64a all arranged in the conventional manner to transmit a beam of light through the fluid mixture passing downwardly through the cell Sila. The operation of the cellsurrounding chamber 51a and overflow outlet 52a in establishing a uniform continuous flow of the mixture under test through the colorimeter 15a is as described above in connection with the FIG. 1 modification.

In order to change the flow rate of the 'trant 12a and thus cause oscillating color changes in the cell Eda, the float valve 36a is vertically adjustable and the output of the colorimeter photoelectric cell 64:: is used to vary the vertical position of the valve 36a and thus vary the head pressure on the titrant at the metering tube 31a. In this way, the flow rate of the 'titrant added to the stream of sample 11a in the passage 24a is varied. In the illustrated construction, the valve 35a is mounted on a bracket 8% that is threaded on a lead screw 81 journalled at 82 and $3 in the analyzer llfla'. The screw 31 is ro= tatably driven by a motor 84 through a .worm 85 and gear 86.

The motor 84 is continuously driven and the photoelectric cell la, through an amplifier 87, drives a relay 38 which controls the direction of rotation of the motor 34 (see P16. 3). In the embodiment shown in FIG. 2, the amplifier 87 and relay 38, together with appropriate fuses and on/ofl switches, are enclosed within a box 89.

To permit the float valvelhia to be raised and lowered by running the bracket 80 up and down the lead screw 81, the conduit 34a is flexible and of a suflicient length to provide the desired range of movement of the float valve.

To illustrate the function of the analayzer itla, it will be assumed that the analyzer has been set up to measure the total hardness of a water stream within a range of zero to 250 parts per million. The titrant 31% is preferably a standard EDTA solution in a concentration suitable forthe selected rangeot hardness. A standard hardness buffer-indicator is used as the indicator ill which normally produces a red color when added to the water- EDTA solution but which turns blue at the titration end point indicating a complete reaction between the water hardness elements and the EDTA solution. A red filter.

63a is employed.

When the operation of the analyzer ltla adjusted as described above is begun, the color in the colorimeter cell Sea is red so that the photoelectric cell 64a receives radiation and produces an electrical output which is ampiiiied by the amplifier $7 and is eifective to operate the relay 88. With the relay 83 picked up, the continuously energized motor 34 is driven in a direction so as to cause the lead'screw 81 to raise the bracket 89 and thus lift the float valve 36a. As the float valve Bea rises, the rate of titrant flow into the passage 24a is increased until the increased amount of titrant causes the titration end point to be reached and the fluid mixture in the cell 59a toturn blue. The filter 63a absorbs the blue light passing through the fluid in the cell Sea so that the photoelectric cell 6dr: ceases to be activated whereupon the relay 88 drops out and the motor 34 is reversed to drive the bracket 8i} and thus the float valve 36a downwardly.

Downward movement of the float valve Eda causes a decrease in the flow rate of the titrant into the passage 24a until the mixture in the cell 5% goes past the end point of the titration reaction and the solution again turns red with the result that the photoelectric cell 64a is again activated and the motor 84- reversed.

The apparatus lda thus embodies a form of oscillating feedback, with the raising and lowering of the valve 35a causing color oscillations in thefluid mixture being sensed in the colorimeter cell Silo. The color oscillations in turn produce the raising and lowering motion of the float valve 36a. In the illustrated embodiment under discussion, it requires about five minutes to produce a reversal of the motor 34 and the range of travel of the float valve 36a is approximately one quarter of an inch. To enable the results of the titration performed by the analyzer ltia to be read directly, a scale 91 and pointer 92 are associated with the vertically movable bracket 8% so as to indicate the position of the float valve 35a and thus the relative head pressure of the titrant 12a. The scale 91 is calibrated so that the position of the valve 36a is translated directly into terms of the amount of unknown in the sample being tested. In the example being discussed herein, the scale 91 thus reads in total hardness values from zero to 250 p.p.m.

So as to obtain an average reading as the valve 36a oscillates up and down, a lost-motion connection is provided between the pointer 92 and the bracket 3b. In the illustrated embodiment, the bracket 39 carries a pin g3 which moves between spaced bumpers 94 and 95 carried by the pointer 92. The pointer is frictionally supported on the scale 91. The spacing between the 7 bumpers 94, 95 is approximately the normal oscillating distance of the float valve 36a, that is, one quarter of an inch in the present example. The pointer 92 thus stands stationary so long as the sample 11a remains constant and the float valve 36:! simply oscillates back and forth. As soon as the amount of unknown changes in the sample 11a, the movement of the float valve 36a is also correspondingly changed and the position of the pointer fiZ is modified to correspond to the change de= tected in the sample 11a;

Alternatively, the scale 91 and pointer $2 combination can be replaced by a slide wire resistor with the sliding contact being carried, by the bracket 86 and the resistance wire extending alongside of the lead screw 81. In this way,'the vertical position of the float valve 36a can be made to control a variable electrical output and this output can be coupled to an electrically-responsive recorder of standard type to produce a continuousrecord of the titration operation performed by the analyzer a.

The analyzer 10a can also be employed, in addition to testing for total hardness in water, for performing silica and alkalinity analysis on water. Itis also obvious that other titration procedures can be automatically and capably performed by the analyzer 10a simply by utilizing proper titrants and indicators.

1. An automatic analyzer for continuously performing a colorimetric test on a fluid sample by using a known testing reagent comprising, in combination, means including a metering pass-age for feeding said sample at a constant head through said metering passage so as to create a steady and uniform stream of said sample, means including a metering passage for feeding said reagent to said sample stream at a predetermined head through said metering passage so as to add to said sample stream a steady and uniform flow of reagent, a colorimeter including a transparent generally vertically disposed cell having an open top and open bottom, a transparent chamber surrounding said cell with the lower end of the cell opening into said chamber, an overflow outlet formed in said chamber above the lower end of said cell, and means for dripping said sample-reagent stream into said cell so as to mix the sample and reagent.

2. An automatic analyzer for performing continuous titration on a fluid sample by using a known titrant and a known indicator comprising, in combination,-means for feeding said sample at a constant head to create a steady and uniform stream of said sample, means for feeding said titrant to said sample stream at a variable head to add to said sample a continuous flow of titrant, means for feeding said indicator to said sample stream at a predetermined head to add to said stream a steady and uniform flow of indicator, a mixing cell, means for mixing said sample-titrant-indicator stream in said cell, means for maintaining a constant and uniform flow of sampletitrant-indicator mixture through said cell, means for' detecting a reaction in said mixture indicative of reaching an end point, and means responsive to said detecting means for varying the head of said titrant so that said head is continuously raised and lowered to repeatedly bring the mixture to end point.

3. An automatic analyzer for continuously performing spectrophotometric titration on a fluid sample by us ing a known titrant and a known indicator comprising, in combination, means for feeding said sample at a constant head to create a steady and uniform stream of said sample, means for feeding said titrant to said sample stream at a variable head to add to said sample a cont-inuous flow of titrant, means for feeding said indicator to said sample stream at a predetermined head to add to said stream a steady and uniform flow of indicator, a mixing cell, means for dripping said sample-titrant-indicator stream into said cell so as to mix the sample, titrant and indicator, means for maintaining a constant and uniform' flow of sample-itrant-indicator mixture through said cell, a colorimeter for detecting a reaction in said mixture indicative of reaching an end point, and means responsive to said colorimeter for varying the head of said titrant so that said head 'is'continuously raised and lowered to repeatedly bring the mixture to end point.

4. An automatic analyzer for performing continuous titration on a fluid sample by using a known titrant and a known indicator comprising, in combination, means including a metering passage for feeding said sample at a constant head through said metering passage so as to create a steady and uniform stream of said sample, means including a metering passage for feeding said titrant to said sample stream at a variable head through said metering passage so as to add to said sample a continuous flow of titrant, means including a metering passage for feeding said indicator to said sample stream at a predetermined head through said metering passage so as to add to said streama steady and uniform flow of indicator, a mixing cell, means for mixing said sampletitrant-indicator stream in said cell, means for maintaininga constant and uniform flow of sample-titrant-indicator mixture through said cell, means for detecting a reaction in said mixture indicative of reaching an end point, means responsive to said detecting means for varying the head of said titrant so that said head is continuously raised and lowered to repeatedly bring the mixture to end point, and a scale for indicating the head of said titrant and thus the amount of titrant required to bring about the end point reaction.

5. An automatic analyzer for continuously performing a colorimetric test on a fluid sample by using a known testing reagent comprising, in combination, a frame defining a fluid passage, a first conduit for conducting a flow of said sample to said passage at a constant head pressure, a first capillary metering tube mounted in said frame and opening at one end into said passage, a second conduit for conducting a constant flow of said reagent to the other end of said first metering tube at a head pressure greater than said sample head, a second capillary metering tube mounted in:said frame and opening into said passage, a colorimeter including a transparent cell, a third conduit coupling the second metering tube with said cell so that said sample and reagent is uniformly dripped into said cell and mixed, means for maintaining a constant and uniform flow of sample-reagent mixture through said cell, and means for indicating the output of said colorimeter.

6. An automatic analyzer for continuously performing a colorimetric test on a fluid sample by using a known testing reagent comprising, in combination, a frame defining a fluid passage extending generally from one end of the frame to the other, a first conduit for conducting a flow of said sample to said passage, an upstanding overflow outlet coupled to said conduit for maintaining a constant head pressure on said sample in said passage, a first capillary metering tube mounted in said frame and opening at one end into said passage,,a second conduit for conducting a constant flow of said reagent to the opposite end of said first metering tube, afloat valve interposed in said second conduit for maintaining a head pressure on said reagent'in said metering tube, said float valve being higher than said overflow outlet so that said reagent head is greater'than said sample head, a second capillary metering tube mounted in said frame and opening at one end into said passage, a colorimeter including a transparent cell, a third conduit coupling the other end of said second metering tube with said cell, said cell being open at the bottom and having an overflow outlet positioned'a'bove the open bottom so as to maintain a constant and uniform flow of sample-reagent mixture through said cell, and means for continuously indicating the output of said cclorirneter.

7. An automatic analyzer for continuously performing a colorimetric test on a fluid sample by using a known testing reagent comprising, in combination, a frame block defining a fluid passage extending generally from one end of the frame block to the other, a first conduit for conducting a flow of said sample to one end of said passage, means coupled to said conduit for maintaining a constant head pressure on said sample in said pasage, a generally vertical first capillary metering tube mounted in said frame block and opening at its lower end into said passage, a second conduit for conducting a constant flow of said reagent to the upper end of said first metering tube, means interposed in said second conduit for maintaining a head pressure on said reagent in said metering tube, a generally vertical second capillary metering tube mounted in said frame block and opening at its upper end into the end of said passage that is opposite said first conduit connection, said frame block being tilted so that said passage slopes downwardly from said first conduit to said second metering tube, a colorimeter including a transparent cell, a third conduit coupling the lower end of said second metering tube with said cell so that said sample and reagent is uniformly dripped into said cell and mixed, means for maintaining a constant and uniform flow of sample-reagent mixture through said cell, and means responsive to the output of said colorimeter for indicating the color sensed by said meter.

8. An automatic analyzer for continuously performing a colorimetric test on a fluid sample by using a known testing reagent comprising, in combination, a frame defining a fluid passage extending generally tfrom one end of the frame to the other, a. first conduit for conducting a flow of said sample to one end of said passage, means coupled to said conduit for maintaining a constant head pressure on said sample in said passage, a strainer mounted in said passage so that the fluid sample flows through the strainer, a generally vertical first capillary metering tube mounted in said frame and opening at its lower end into said passage, a second conduit for conducting .a constant flow of said reagent to the upper end of said first metering tube, means interposed in said second conduit for maintaining a head pressure on said reagent in said metering tube, said reagent head being greater than said sample head, a generally vertical second capillary metering tube mounted in said frame and opening at its upper end into the end of said passage that is opposite said first conduit connection, a colorimeter including a transparent cell, a third conduit coupling the lower end of said second metering tube with said cell, means for maintaining a constant and uniform flow of sample-reagent mixture through said cell, and means responsive to the output of said colorimeter for indicating the color sensed by said meter.

9. An automatic analyzer for continuously performing spectrophotometric titration on a fluid sample by using a known titrant and a known indicator comprising, in combination, a frame defining a fluid passage, a first conduit for conducting a flow of said sample to said passage at a constant head pressure, a first capillary metering tube mounted in said frame and opening at one end into said passage, a second conduit for conducting a constant flow of said titrant to the other end of said first metering tube at a variable head pressure, -a second capillary metering tube mounted in said frame and opening at one end intosaid passage, a colorimeter including a transparent cell, a third conduit coupling the other end of said second metering tube with said cell, a third capillary metering tube mounted in said frame and opening at one end into said third conduit, means for conducting a constant flow of said indicator to the other end of said third metering tube at a head greater than said sample head, means for maintaining a constant and uniform flow of sampletitrant-indicator mixture through .said cell, means responsive to the out-put of said colorimeter for controlling said titrant head so that said head is continuously raised and lowered to vary the titrant flow rate and cause oscil- 'lating color changes in saidlsample-titrant-indicator mixture in said cell, and a scale and indicator for showing the amount of tit-rant required to bring about the end point color changes in said cell.

1%). An automatic analyzer for continuously performing spectrophotometric titration on a fluid sample by using a known titrant and a known indicator comprising, in combination, a frame defining a fluid passage, a first conduit for conducting a flow of said sample to said passage at a constant head pressure, a first capillary metering tube mounted in said frame and opening at one end into said passage, a second conduit for conducting a constant flow of said titrant to the other end of said first metering tube, means interposed in said second conduit for establishing a variable head pressure on said titrant in said metering tube, a second capillary metering tube' mounted in said frame and opening at one end into said passage, a colorimeter including a transparent cell, a third conduit coupling the other end of said second metering tube with said cell, a third capillary metering tube mounted in said frame and opening at one end into said third conduit, means for conducting a constant flow of said indicator to the other end of said third metering tube at a head greater than said sample head, means for maintaining a constant and uniform flow of sample-titrant-indicator mixture through said cell, means responsive to the output of said colorimeter for controlling said titrant head establishing means so that said head is continuously raised and lowered to vary the titrant flow rate and cause oscillating color changes in said sample-titrant-indicator mixture in said cell, and a scale and indicator coupled to said titrant head establishing means through a lost-motion connection for indicating the average position of the titrant head and thus the amount of titrant required to bring about the end point color changes in said cell.

11. An automatic analyzer for continuously performing spectrophotometric titration on a fluid sample by using a known titrant and a known indicator comprising, in combination, a frame defining a fluid passage extending generally from one end of the frame to the other, a first conduit for conducting a flow of said sample to one end of said passage, means coupled to said conduit for maintaining a constant head pressure on said sample-in said passage, a strainer mounted in said passage so that the fluid sample flows through the strainer, a first capillary metering tube mounted in said frame and opening at one end into said passage, a second conduit for conducting a constant flow of said tit-rant to the other end of said first metering tube, means interposed in said second conduit for establishing a variable head pressure on said titrant in said metering tube, a second capillary metering tube mounted in said frame and opening at one end into the end of said passage that is opposite said'first conduit connection, -a colorimeter including a transparent cell, a third conduit coupling the other end of said second metering tube with said cell, a third capillary metering tube mounted in said frame and opening at one end into said third conduit, means for conducting a constant flow of said indicator to the other end of said third metering tube, means for maintaining a constant and uniform flow of sample-titrant-indicator 'mixture through said cell, means responsive to the output of saidcolorimeter for controlling said titrant head establishing means so that said head is continuously raised and lowered to vary the titrant flow rate and cause oscillating color changes in said sample-titrant-indicator mixture in said cell, and a scale and indicator associated with said titrant head establishing means to indicate the titrant head and thus the amount of titrant required to bring about the end point color changes in said cell.

nent of a flowing sample stream comprising, in'combination, a first capillary tube adapted to be open to said sample stream for discharging a regulated flow of sample, means containing a supply of reagent, a second capillary tube connected to said supply of reagent for discharging a regulated flow of reagent, means defining a zone of reaction open to' said flow of said sample and said flow of said reagent, and means adjacent said zone for detecting a reaction resulting from the mixing of said sample and said reagent in said zone of reaction.

References Cited by the Examiner UNITED STATES PATENTS Re. 24,553 10/58 Krasl etal 23253 1,333,905 3/20 Delm 23230 12 2,095,056 10/ 37 Clough 23253 2,102,282 12/37 Roy 23253 2,161,453 6/39 Busby 23-253 2,248,765 7/41 Langelier 23230- 2,627,453 2/53 Sheen 23253 2,692,764] 10/54 Hanson 259-4 2,747,844 5/56 Slayter 2594 2,797,149 1/57 Skeggs 23253 2,977,199 3/61 Quittner 23230 3,010,800 11/61 Whitehead et a1. 23253 3,026,182 3/62 Jankowski et a1. 23230 MORRIS O. WOLK, Primary Examiner.

15 MAURICE A. BRINDISI, GEORGE D. MITCHELL,

ANTHONY SCIAMANNA, Examiners. 

1. AN AUTOMATIC ANALYZER FOR CONTINUOUSLY PERFORMING A COLORIMETRIC TEST ON A FLUID SAMPLE BY USING A KNOWN TESTING REAGENT COMPRISING, IN COMBINATION, MEANS INCLUDING A METERING PASSAGE FOR FEEDING SAID SAMPLE AT A CONSTANT HEAD THROUGH SAID METERING PASSAGE SO AS TO CREATE A STEADY AND UNIFORM STREAM OF SAID SAMPLE, MEANS INCLUDING A METERING PASSAGE FOR FEEDING SAID REAGENT TO SAID SAMPLE STREAM AT A PREDETERMINED HEAD THROUGH SAID METERING PASSAGE SO AS TO ADD TO SAID SAMPLE STEAM A STEADY AND UNIFORM FLOW OF REAGENT, A COLORIMETER INCLUDING A TRANSPARENT GENERALLY VERTICALLY DISPOSED CELL HAVING AN OPEN TOP AND OPEN BOTTOM, A TRANSPARENT CHAMBER SURROUNDING SAID CELL WITH THE LOWER END OF THE CELL OPENING INTO SAID CHAMBER, AN OVERLFOW OUTLET FORMED IN SAID CHAMBER ABOVE THE LOWER END OF SAID CELL, AND MEANS FOR DRIPPING SAID SAMPLE-REAGENT STREAM INTO SAID CELL SO AS TO MIX THE SAMPLE AND REAGENT. 